The present invention relates to a pair of water pump pliers, consisting of two pincer parts crossing themselves in a connecting region, each consisting of a handle portion and a jaw, wherein the pincer parts are movably connected in the connecting region in such a way, that the first pincer can be displaced relative to the second pincer to adjust a jaw opening-width that is needed for gripping or is optimal at the present time on the one hand, and that the pincer parts for grabbing with the jaws can reciprocally pivot on the other hand, wherein blocking means are provided in such a manner that further shifting of the first pincer part is blocked when the jaws stop against a workpiece to be gripped, and wherein a spring element is installed between the handles of the pincer parts in such a way, that a releasing force from the spring, operating in the jaws"" opening direction, acts upon the pincer parts.
A pair of water pump pliers of this type is known from DE-AS 2031661. These pliers are supposed to be easy to operate with only one hand, but this is only partially achieved, however. Starting with a completely open opening width between the jaws, they can indeed be automatically brought into the most favorable clamp setting in contact with the object or workpiece to be clamped by single-handed manipulation, i.e. by simply pressing the handles together with one hand. In this clamp setting, a detent pawl, which can shift and pivot within an elongated hole and which is provided as blocking means, is also blocked automatically. If the manual pressure is released, however, this simply causes the jaws to release the object and the blocking means to loosen. But then the pincer parts remain in this position, so that they have to be moved manually into the largest jaw opening-width by shifting them relative to each other, and this can only be done with two hands. Structurally, this is due to the fact that the spring element installed between the handles is designed as a hairpin-like spring washer or wound pivot spring, whose one end is rigidly and immovably attached to one handle. But the spring""s other end abuts loosely on the other handle in such a way that this pincer part can be displaced relative to the adjacent end of the spring, whereby the pincer part can pivot around its point of contact with the spring like a seesaw. In this manner, the spring can indeed press the handles apart to release both the clamped object and the blocking means, but it won""t cause the jaws to move into their fully open position.
A xe2x80x9ctruexe2x80x9d pair of single-handed water pump pliers is indeed known from U.S. Pat. No. 4,651,598 and/or the parallel EP 0218760B 1, since this pair of pliers does automatically return into a fully opened position after clamping. However, this is achieved by means that are extraordinarily expensive structurally. Instead of a simple spring element (as in the above publication that establishes a species), a special rigid control arm is installed between the handles in this known pair of single-handed pliers. This arm is linked to one handle so that it can pivot and attached to the other handle so that it can be displaced. A special spring device with several individual spring elements is also provided for automatic sequence of motion. This design consequently results in a very large cost for components and assembly, which consequently causes quite high manufacturing expenses, especially for accommodating the spring elements partially within the handles.
It is the objective of the present invention to proceed from the state of the art described in the introduction and create water pump pliers of this type with xe2x80x9ctruexe2x80x9d single-hand operation, which are distinguished by a particularly simple design and small manufacturing costs, few parts and simple assembly in particular.
This is achieved in accordance with the invention by designing the spring element and connecting it with the handle portions of the two pincer parts in such a way that the spring element, in addition to generating the releasing force, also acts upon the first pincer part with a torque directed around a spring fastening point in such a way that, by a corresponding shift of the first pincer part relative to the second pincer part, the jaws automatically move into a fully opened opening width following a manual release (letting-go of the handles to terminate the gripping). In accordance with the invention, the two handles are consequently connected exclusively by one simple one-piece spring element, which advantageously performs multiple functions, however, due to its development in accordance with the invention and its special means of attachment to the handles. The spring element thus generates the releasing force, which presses the handles apart to open jaws after the handles have been manually loosened or released, yet the spring element in accordance with the invention also applies a torque upon the first pincer part in such a manner that the part is shifted within the connecting region until the jaws have been opened completely as wide as possible.
A particularly simple and inexpensive design consists of, that the spring element is designed as a one-piece curved flat spiral spring whose first end is rigidly attached to the handle of the second pincer part and whose second end, located at the end of a curved spring segment that is spiraled to generate a torque, is rigidly attached to the handle of the first pincer part, i.e. torque-positive on one side and immobile on the other side, even viewed from the handle""s longitudinal direction. Moreover, the spiral-shaped spring segment works like a clock spring, generating the torque that is provided to attain the completely opened position, whereas the remaining section of the spring, extended between the handles, mainly generates the releasing force. It is preferable for the spring element in accordance with the invention to be elastically deformable in such a way, that it causes all essential relative motions of the pincer parts or that they are at least possible.
Additional preferable characteristics of the invention are contained in the dependent claims and in the following description: